1. Field of the Invention
This invention relates to a jig, fixture, or tool for use in removing an old or worn chain from an apparatus with which it is engaged and for replacing the worn chain with a new chain. The device of the invention, while not restricted to such use, will be described as embodied for use in connection with the replacement of a timing chain of an internal combustion engine, particularly an internal combustion engine of the overhead cam type.
2. Description of the Prior Art
It has been known in the prior art relating to chain replacement, such as the replacement of timing chains on internal combustion engines of the overhead cam type, for example, to disconnect the old or worn chain intermediate of its length, while the old chain is still in place about the various sprockets which it usually engages, and to connect the new chain in series with the old chain by means of a detachable master link at the leading end of the new chain, with the opposite end of the master link being connected to the trailing end of the old chain. The crankshaft of the engine is then manually rotated to cause both the new and old chains to be pulled along the chain path about the various toothed sprockets along the path of movement of the chains until the entire length of the new chain has been pulled into the chain path, and the entire length of the old chain has exited or been discharged from the chain path, at which time the old chain is disconnected from the new chain and the two ends of the new chain are connected together by means of the master link to thereby complete the installation of the new chain. The prior art method of removing an old chain and replacing it with a new chain as just briefly described has various problems which have made it an unsatisfactory method of replacing the old chain with the new chain.
Thus, for example, the prior art method of chain replacement as just briefly described is very time consuming and normally requires the use of at least two persons to perform the chain replacement operation. Furthermore, when the chain which is being replaced is the timing chain of an internal combustion engine which drives the cam shaft of the internal combustion engine, the manual replacement process hereinbefore described makes it very difficult to insure that the proper timed relation is maintained between the cam shaft and the pistons of the internal combustion engine since if any slippage occurs during the manual chain replacement process hereinbefore described, the timed relation between the cams which control the fuel inlet and exhaust valves of the engine and the pistons of the engine may be lost.
Furthermore, in the prior art manual chain replacement method hereinbefore described, the extensive direct contact of the workmen with the chain sprockets and with the chain may at times present safety hazards resulting in injury to the operating personnel. Also, the prior art method of manually replacing the chain can possibly cause damage to the engine or other machine on which the chain is being replaced and/or to the chain itself. In the prior art method of chain replacement, it is possible for the chain to become disengaged from the drive sprocket on the crankshaft, in which case it is very difficult and time consuming to re-engage the chain with the crankshaft drive sprocket.
Although an extensive search was made through the records at the U.S. Patent and Trademark Office, no patent or other publication was noted which appears to be pertinent with respect to applicant's invention which relates to a tool or fixture for use in the in situ replacement of an old, or worn chain with a new chain.